PLC Database Request Retransmission After Connection Errors
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Solution Overview
Problem
Existing controllers, such as PLCs, face challenges in flexibly recovering from errors in database connection, as they often lack efficient mechanisms to retransmit specific access requests that failed due to connection errors.
Innovation Solution
A controller is designed with an access processing unit that extracts and retransmits access requests, such as SQL statements, from an error list based on prescribed conditions, allowing for flexible recovery from database connection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all access requests are retransmitted when database connection fails, then recovery completeness is improved, but unnecessary retransmissions increase causing system inefficiency
Solution Approach 1:
The patent extracts only the necessary access requests from the error list based on prescribed conditions (such as request type, timing, or frequency criteria) rather than retransmitting all failed requests. This selective extraction ensures that only relevant requests are retransmitted, improving system efficiency while maintaining recovery completeness for critical operations.
2Loss of time
If access request retransmission is fully automated, then recovery speed is improved, but flexibility in handling different error scenarios deteriorates
Solution Approach 1:
The patent implements a dynamic retransmission mechanism where the retransmission behavior adapts based on prescribed conditions that can be configured for different error scenarios. The system can adjust retransmission parameters such as timing, target requests, and retry counts based on the specific error context, thereby maintaining both speed and flexibility.
Solution Approach 2:
The patent allows modification of retransmission parameters (such as which requests to retransmit, when to retransmit, and how many times) based on the error conditions and user-defined prescriptions. This parameter-based control enables the system to optimize recovery speed for different scenarios while maintaining the ability to handle diverse error situations flexibly.
3Device complexity
If no conditions are applied to access request retransmission, then processing simplicity is improved, but inappropriate retransmissions occur causing data consistency issues
Solution Approach 1:
The patent segments the error list into different categories of access requests based on prescribed conditions (such as request type, timing, or criticality). By dividing the retransmission task into segments with specific criteria, the system maintains processing simplicity through automated classification while ensuring data consistency by applying appropriate retransmission rules to each segment.
Data Source
AI summary
A controller for controlling a control object includes a communication interface, an instruction executor, and an access processor. The communication interface accesses a database device. The instruction executor executes a user program including an access instruction for accessing the database device, the user program being associated with control of the control object. The access processor generates an access request in response to execution of the access instruction and causes the communication interface to transmit the access request. The access processor extracts an access request satisfying a prescribed condition from an error list including access requests recorded when access to the database device fails and causes the communication interface to retransmit the access request extracted.